1. Field of the Invention
The present invention relates to plate member joining structures and more particularly, to a plate member joining structure formed of a metal plate member and a plastic plate member that are joined together by insert molding to avoid separation.
2. Description of the Related Art
Following fast development of science and technology, the design concept of commercial electronic products is focused on light, thin, short and small characteristics. Many electronic products (cell phone, notebook, PDA, etc.) are made convenient to carry by user. To enhance mobility, the weight of electronic products must be reduced. In order to reduce the weight, the shell or casing of an electronic product may be formed of an outer metal layer having a relatively thinner wall thickness and an inner plastic layer having a relatively thicker wall thickness. This design greatly reduces the product weight while providing excellent tensile strength. Further, the outer metal layer facilitates surface treatment by an electroplating or coating technique. Therefore, metal is commonly used for the casing or the outer layer of the casing for commercial electronic products.
When setting a plastic plate member in a metal plate member to give a support, an adhesive is usually used to bond the two plate members together. However, this method has drawbacks as follows:
1. The metal plate member and the plastic plate member are separately made, complicating the manufacturing process and increasing the manufacturing cost.
2. After hardened, the volume of the adhesive is slightly reduced (due to vaporization of fluid), and tiny open spaces may exist in between the metal plate member and the plastic plate member, lowering the product yield rate.
3. The metal plate member and the plastic plate member may be twisted when the user opens or closes the electronic product, and the torsional force thus produced may cause separation of the adhesive from the metal plate member and/or the plastic plate member, resulting in plate member separation damage.
4. When bonding the metal plate member and the plastic plate member together, the hardening time of the applied adhesive prolongs the product manufacturing time. Further, the use of the adhesive relatively increases the manufacturing cost of the product, weakening the competitive advantage.